British Antarctic Survey
Ozone Bulletin 13/96 issued 1997 August 15



This bulletin summarises the 1996 – 1997 Antarctic season and presents total column ozone measurements made using Dobson ozone spectrophotometers. Note that all ozone values are preliminary and are subject to revision from time to time when the instrument constants are re-evaluated. All ozone data is reduced to the Bass-Paur scale as recommended by the WMO.


I have recently updated the BAS ozone web page, which contains earlier bulletins, data and general ozone information. The url is:

http://www.nbs.ac.uk/public/icd/jds/ozone



1. Data from the British Antarctic Survey (BAS) Halley station (76-deg south, 26-deg west, on the Brunt ice shelf).


a) Ozone. Routine ozone measurements from Halley station do not start until towards the end of August because the sun is not high enough to permit measurements. Mean total ozone values fell from an estimated 260 DU in early July to around 140 DU in mid September and then declined more slowly to reach 125 DU in early October. They climbed to around 180 DU by late October, but remained at that level throughout November. In early December, ozone levels began to rise and reached a peak of around 300 DU late in the month. This is some 80 DU lower than the pre-ozone hole average peak value. After that, values slowly declined and had reached around 230 DU by the end of the season. Values only briefly exceeded the lower bound of the variation from the long-term mean late in the season. The lowest mean daily value seen (114 DU on October 8) is comparable to that of the previous few years. Note that contrary to some reports [WMO Bulletin 46, No 2, 1997 April] this is not the lowest value ever recorded at Halley.


Halley preliminary mean daily total ozone, (DU)
Dobson No 103: Instrument constants revised 1997 May 2.
(0 indicates no data)


1996 August 1 - 1997 April 30


0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 174 177 174 170 167 169

202 177 177 183 206 168 156 181 200 172

159 162 143 137 128 124 134 179 153 132

135 135 132 130 149 142 151 131 128 146

153 136 125 119 119 117 133 114 144 139

125 119 130 129 126 126 130 126 147 192

207 164 147 142 153 217 192 189 208 200 163

161 160 172 179 185 220 188 158 158 155

166 170 177 155 198 230 174 167 170 172

180 194 205 203 184 187 178 185 189 203

172 163 160 171 182 191 201 227 239 261

273 275 273 260 268 260 273 298 303 298

291 298 300 313 318 313 306 305 272 293 296

290 318 306 295 284 294 309 301 288 283

287 267 278 291 285 260 267 284 275 265

267 272 264 262 258 265 265 255 261 256 260

271 263 265 280 284 279 282 297 288 289

295 287 266 246 247 240 247 259 251 241

239 240 260 253 248 254 270 281

257 254 276 260 251 242 222 245 266 254

257 244 244 246 227 243 241 236 244 232

223 237 259 265 247 240 256 237 242 219 239

254 269 259 261 272 249 255 261 237 229

233 212 229 217 239 0 0 0 0 0

0 0 224 224 242 236 0 0 0 0

 


Halley provisional monthly mean total ozone (DU)


Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year

1996/97 172 155 149 181 260 278 265 245 242 216

1995/96 219 160 129 163 253 263 248 247 224 210

1957-72 295 285 300 355 350 320 300 295 285 310


The September monthly mean is the lowest recorded for the month. The minimum value recorded during December (160 DU) exceeded the previous minimum for the month by a substantial margin.

b) Radiosonde data. Stratospheric temperatures at 100 hPa, near the peak of the ozone layer, can be used to reflect changes in ozone amount. Stratospheric clouds, which are crucial to the mechanism of ozone depletion, are likely to be present when the 100 hPa temperature is below -80 deg C and may persist whilst the temperature is below -75 deg C. Data from Halley show that the 100 hPa temperature rose during October from -83 deg C to reach -73 deg C at the end of the month, which is about 8 C deg below the long term mean. The temperature increased slowly through November to reach -70 deg C (some 25 deg C below the long term mean) and the final warming began in early December. The temperature at 100 hPa remained substantially below the long-term mean until it peaked at -38 deg C on the 27th. For most of the first half of 1997 it was close to, though a little below the long-term mean.



2. Data from the Ukrainian Antarctic Research Centre Vernadsky station (65 south, 64 west off the coast of the Antarctic Peninsula, formerly the BAS Faraday station).

Routine ozone measurements commence at Vernadsky in early August, but some observations, of lower accuracy, are made in July. Mean total ozone values fell from an estimated 290 DU in early July to 190 DU in early August. The total ozone fell to exceptionally low values, below 140 DU, on August 4th and low values were also recorded around the 7th and 28th. The previous minimum mean daily value recorded during August was 170 DU in 1992. Long period planetary wave activity gave total ozone peaks of around 240 DU in mid August and late September and troughs of around 160 DU in mid September and 210 DU in mid October. After late September, short period planetary waves were active and day to day variation was around 100 DU until early November when it dropped to around 20 DU. Mean ozone levels rose to around 380 DU in early November, but then dropped back to ozone hole levels of around 200 DU for the remainder of the month and into December. The final rise started around December 8th and reached summer levels by early January, though values remained around 5 - 10% down on the long term mean until the end of the ozone season.


Vernadsky preliminary mean daily total ozone (DU).
Dobson No 31: Instrument constants revised 1997 August 15


1996 August 1 - 1997 April 30


222 211 177 150 186 214 174 190 212 233 229 233 225 244 223 240 243 238 226 239 239 246 235 258 226 206 192 189 186 227 209 232 253 222 193 188 179 185 175 149 179 184 167 156 182 182 159 138 172 180 193 240 245 294 291 246 252 190 208 283 247

224 191 197 166 177 185 226 281 209 202

248 325 306 286 209 197 161 167 326 347

361 369 217 233 358 353 338 347 345 352 262

286 325 375 382 374 282 247 210 197 180

186 196 178 186 179 179 191 224 233 208

205 190 181 181 177 181 191 205 217 223

227 199 180 204 217 230 235 247 303 306

311 311 331 301 270 257 252 255 265 270

277 289 283 279 281 284 297 311 300 317 315

304 324 312 318 328 319 316 323 318 319

308 312 315 295 310 312 310 289 267 284

298 269 307 291 303 304 308 295 297 283 282

288 296 295 288 286 280 303 296 295 271

277 273 277 279 286 279 286 269 265 279

277 279 274 272 266 251 275 249

304 275 263 291 286 269 261 257 255 294

324 246 280 259 218 237 290 265 277 282

285 311 293 267 265 262 281 295 303 289 300

263 287 272 276 287 306 335 316 302 308

292 272 261 265 279 285 282 267 268 291

284 283 296 312 346 351 316 331 290 294

 

Vernadsky provisional monthly mean total ozone (DU)


Period Aug Sep Oct Nov Dec Jan Feb Mar Apr Year

1996/97 217 205 263 226 271 304 279 277 294 260

1995/96 237 194 251 228 298 285 287 278 266 258

1957-72 310 330 345 370 345 320 300 295 310 325


The data suggest that the instrument constants may still require some further revision. The August monthly mean of 217 DU is the lowest for that month by a substantial margin, the previous lowest was 236 DU in 1992. The November monthly mean is the lowest for that month, though it is comparable to the value over the past few years. The December minimum value of 180 DU is the lowest on record for the month; the previous minimum was recorded in 1990, which had a comparable monthly mean to 1996.


3. Other information


I visited the British Antarctic Survey Rothera station (68-deg south, 68-deg west, on Adelaide Island) during November and December of 1996. When I left the UK, in early November, ozone values over the Antarctic Peninsula appeared to have returned to summer values. On the voyage between the Falkland Islands and Rothera we stopped at Port Lockroy (65-deg south, 64-deg west, off the coast of the Antarctic Peninsula), to land supplies at the station. There was hazy sunshine through a layer of cirrostratus clouds. I took my usual precaution of applying factor 15 barrier cream, but despite this was mildly sun-burnt. Others who took no precautions were severely sun-burnt. A radio-sonde flight the next day showed that the 100 hPa temperature was below -70 deg C, confirming my suspicion that ozone hole conditions had returned and that consequently, high uv levels were present. This return of low ozone levels to the Peninsula region in November is shown by the Vernadsky data and also by TOVS and TOMS maps. First hand experience of increased uv associated with ozone depletion, is a much more effective lesson than any amount of theoretical prediction.



If you use or pass on this data please make acknowledgement to J D Shanklin, British Antarctic Survey.